In the Ullambana Sūtra《盂兰盆经》is record of the origin of the Ullambana Festival or Day (盂兰盆节). When Mahamaudgalyāyana (摩诃目犍连; Maha Moggallāna) attained his supernormal powers, he searched for his deceased Mother’s whereabouts to repay her kindness, and saw that she had been reborn as a hungry ghost without food and drink, with nothing but skin and bones. With grief and empathy, he filled a bowl with food for her, which she reached for. However, before a handful could enter her mouth, the food turned into burning coals. Even being the Arhat foremost with supernormal powers, he could not feed her.

Weeping sorrowfully, Mahamaudgalyāyana rushed to the Buddha to request for help. The Buddha explained that as his Mother’s negative karma was very strong, even with Mahamaudgalyāyana’s (great but still limited) power, and cries which move the gods and ghosts, they too do not have enough power to help. However, when the virtuous Saṃgha community of the ten directions (everywhere) assemble, their united power is able to facilitate her liberation from suffering. This can be done through the collective meritorious power of making offerings to the Triple Gem (to the Buddhas through the Saṃgha, with the sharing of the Dharma to aid many beings).

As the 15th day of the 7th lunar month is Pravāraṇā Day (僧自恣日), for monastics’ self-confession and repentance, also known as the Day Of Buddha’s Joy (佛欢喜日), when monastics congregate after the rains retreat to report of their spiritual progress, the occasion should also be used to reverently make extensive food and other practical offerings of various necessities to all present, on the behalf of present and past parents. (It is easier to make more offerings with many doing so collectively.) That day, even great Bodhisattvas will manifest as monastics to partake of the offerings, thus allowing donors to create great meritorious virtues.

Dedicating such merits to express filial piety, one’s present and past parents of seven generations, with one’s close relatives, will be able to eradicate their karmic obstacles, to escape the suffering of the three lower realms of hell-beings, hungry ghosts and animals, with clothing and food spontaneously appearing. Parents alive will have health and longevity without suffering, and past parents will be joyfully reborn in higher realms of humans or gods. (To reach Amitābha Buddha’s [阿弥陀佛; Āmítuófó] Pure Land [净土], there must be guiding with the Three Provisions of Faith in Āmítuófó and his Pure Land, Aspiration to reach it, and the Practice of sincere mindfulness of his name.)

The Buddha also instructed the Saṃgha present to first recite mantras and vows (which is the offering of the Dharma) for the donors’ families. After accepting the food, before personally partaking, it is first offered to the Buddhas (which creates even more meritorious virtues). Doing so accordingly, Mahamaudgalyāyana’s Mother attained liberation from one kalpa (i.e. world cycle) of suffering as a hungry ghost, getting a better rebirth. Thus marked the beginning of the annual Ullambana Festival, which is conducted with some variations worldwide today, on and near the actual day. (Everyday meals can also be offered to Buddhas and the Saṃgha on behalf of all beings too. Although both traditionally do not eat after noon, one can think of those residing beyond the current time zone.)

若一切佛弟子，
应常奉持是法。

– 释迦牟尼佛
《盂兰盆经》

If [as] all [of] Buddha’s disciples,
[they] should constantly uphold this Dharma.